Carbon sequestration in pasture and forage systems

1. Carbon sequestration in pasture and forage systems A. Moulin, P. McCaughey, D. McCartney, S. Bittman, M. Entz, W.F. Nuttall

2. Carbon sequestration in rotations with forages and pastures • Background • Objectives • Methods • Carbon sequestration in rotations with forages • Carbon sequestration in fertilized and unfertilized pasture systems

3. Definitions • Greenhouse gases: nitrous oxide (N2O), methane (CH4), carbon dioxide (CO2) • Carbon Sequestration: Carbon stored in the soil as soil organic matter • Carbon Storage: Carbon stored in the soil as plant debris, roots, and soil organic matter • One tonne of carbon removes 3.667 tonnes of CO2

4. Carbon Sequestration in forages • Increases of 5.4 and 9.3 Mg ha-1 in soil organic carbon (SOC) over 27 years for two studies in smooth bromegrass grassland. (Malhi et al. 1997, Nyborg et al 1994, 1998) • 1.2 to 2.0 Mg C ha-1 yr -1 were stored on soils with poor fertility (Agro.Manger Sept 99 p 7-8) • 0.2 Mg C ha-1 yr -1 over 20 years for intensive management of grassland. (Bruce et al 1999)

5. Objective • To report organic carbon sequestered in pasture systems and rotations with forages. • Discuss issues related to carbon sequestration in forage systems and pastures

6. Carbon Sinks Tap Sink Drain Soil Atmosphere Atmosphere Management Management Fertilizer Rotation Forages Tillage Residue

7. Annual Cropping Systems • Comparison of zero and conventional tillage at 200 locations in the Brown, Dark Brown, and Black soils in Saskatchewan • Approximately 150 sites with a field comparison, 45 replicated studies, 5 detailed studies

8. Current Estimates of Carbon Sequestration • Published literature for zero vs conventional tillage indicates 0.2 Mg C ha-1 yr-1 over 15 years for agricultural soils • Research shows higher levels possible for Black soils over 15 years

9. Annual Crops (15 years) Texture No - till vs Continuous Conventional crop from - 1 - 1 (Mg C ha yr ) Crop - Fallow - 1 (Mg C ha - 1 yr ) Coarse (sand) 0.2 0.5 - 0.6 Medium 0.3 0.5 - 0.6 (loam) Fine (clay) 0.4 0.5 - 0.6

10. Carbon Sinks Tap Sink Drain Soil Atmosphere Atmosphere Management Management Fertilizer Rotation Forages Tillage

11. Forage Studies • Forages in Rotation • Melfort, Saskatchewan • Glenlea, Manitoba • Pasture Systems • Pathlow, Saskatchewan • Brandon, Manitoba

12. Melfort Rotations • Established in 1957 at Melfort, Saskatchewan • Silty clay soil, Thick Black soils • Fertilized and unfertilized Fallow-Wheat-Wheat-Brome Alfalfa Hay- Brome Alfalfa Hay-Wheat

14. Carbon Sinks Tap Sink Drain Soil Atmosphere Atmosphere Management Management Fertilizer Rotation Forages

15. Glenlea Rotations • Established in 1993 at Glenlea, Manitoba • Clay soil, Thick Black soils • Rotations 1) wheat-pea-wheat-flax (W-P-W-Fl); 2) wheat (under seeded to sweet clover)-wheat-flax (W.Cl-W-Fl); 3) wheat- alfalfa (two years)-flax (W-Al-Al-Fl); and 4) a restored native tallgrass prairie • Flax phase was sampled in 1999

17. Carbon Sinks Tap Sink Drain Soil Atmosphere Atmosphere Management Management Fertilizer Rotation Forages

18. Pathlow Pasture • Established in 1978 at Pathlow, Saskatchewan • Undifferentiated medium to moderately fine textured soil, Gray soils • Treatments 0, 45, 90, 180 Kg ha -1 N; 0, 20 kg ha-1 P; 0, 23, 45 kg ha-1 elemental S • Sampled in 1989 and 1999

22. Carbon Sinks Tap Sink Drain Soil Atmosphere Atmosphere Management Management Fertilizer

23. Brandon Pasture • Established in 1994 at Brandon, Manitoba • Fine sandy loam soil, Black soils • Treatments fertilized and unfertilized bromegrass, fertilized and unfertilized alfalfa and bromegrass • Fertilizer applied at soil test recommendations • Sampled in 1999

25. Carbon Sinks Tap Sink Drain Soil Atmosphere Atmosphere Management Management Fertilizer Forages

26. Carbon Sequestration in forages • Potential carbon sequestration ranged from 5 to 15 Mg C ha-1, over a period from 15 to 20 years, depending on fertility management of forages in pasture and initial levels of soil organic carbon.